In the course of modern well logging operations it is conventional to generate digital measurements of preselected logging parameters at a remote well site which are stored on magnetic tape. This information is then transferred to a central data processing location wherein the data may then be more conveniently transformed into a form suited to the particular needs of the end user. Such transfer is typically made by means of a physical transporting of the digital data tapes. Alternatively, however, with the advent of readily available telemetry links, the data may be transferred for further processing at another location by such a link from the remote situs of the well to the processing center.
A serious problem with such a procedure is the significant time delays frequently encountered before the data in final format reaches the end user, such delays in many cases being on the order of days. Often this is because the resulting processed log must then be hand delivered or mailed to the location of the end user from the processing center, such as in a customer's well-log analysis offices across the country.
Delay can further be caused by the fact that the wellsite may be far distant from the data processing center as, for example, in the case of offshore operations. These delays can be extremely expensive inasmuch as equipment and personnel are idled at the wellsite and logging or drilling operations suspended until decisions based upon the processed well logging data can be made.
With the advent of modern computerized digital well logging trucks, wellsite data processing capability is now a reality. However, the problem of getting the visual representation of the log to the end user quickly is still a problem.
Yet another problem has been that even when the user is provided with data in a relatively timely fashion at a remote location, it is frequently desirable to request additional data or other processed versions of the data based upon initial review thereof. This, in turn, necessitates yet additional travel time of the new data from the location where the data processing occurs to the end user, adding additional delay and expense.
Accordingly, techniques have long been sought for providing more immediate access to processed well logging data by the end user as well as a means for providing a real-time link between the end user and the originating source of the data.
In an effort to solve the aforementioned problems, attempts have been made to provide portable data terminals such as the familiar facsimile machines at the remote location where the processed logging data is required, thus obviating the need for physical delivery thereof. In this manner, the processed data may be transferred electrically to the user over available data links such as telephones, telemetry, or the like. Several additional serious problems have been associated with these attempts however.
First, such facsimile machines typically produce pages at a time rather than a continual production of a visible indication of a well log, and thus the operator must periodically tape together segments of a log end-on-end.
Second, the amount of data associated with typical well logging information which must be thus transmitted can be extremely dense. For example, oftentimes fifteen or more curves of logging parameters constitute a well log. Associated with these curves will be numerous graphics, such as alpha-numeric depth or parameter indications, or graphics such as depth lines and the like. Moreover, logs may typically be generated over 5000 foot depth increments of borehole or more, with such parameters being measured as frequently as every 64th of a foot.
In many remote locations of the end user, the only practical link between the source of the digital logging tape (whether it be a digital well logging truck or a data processing center) and the end user is a conventional switched telephone line which is notorious for problems associated with attempting to transmit high data rates thereon. However, conventional facsimile machines must operate at relatively high data transmission or baud rates such as 9600 or the like in order to attempt to accommodate the high information density. Moreover, such machines typically have limited error detection schemes whereby when the telephone line quality deteriorates, significant error is introduced into the end product of the transmitted well log.
In an attempt to alleviate this problem, time consuming error detection schemes conventionally known in the art might be incorporated whereby such machines might drop to a lower baud rate so as to avoid some of the error. However, due to the information formatting associated with such available machines, the time required to transmit a visible representation of a meaningful portion of a well log would be prohibitive.
Accordingly, a method and apparatus for transferring processed well logging data from one location to another was needed whereby the equipment to be positioned at the remote receiving end could be readily portable and easy to operate. Moreover, such methods and apparatus were desired wherein the time required to transmit such vast amounts of data could be significantly reduced without introducing substantial error into the end product, and wherein such data may be transmitted at lower baud rates of 1200 or the like over conventional and readily available telephonic links, thus avoiding the problems associated with higher baud rates.
These and other disadvantages of the prior art are overcome by the present invention wherein an improved method and apparatus is provided for handling digital well logging data.